Portable subsea well service system

ABSTRACT

A technique facilitates a subsea operation such as a well intervention operation. A system comprises a station movably positioned at a subsea location. The station comprises a housing and a lifting arrangement mounted on the housing to enable lifting of the station and movement of the station from one subsea location to another to enable successive subsea operations. The station further comprises a docking station which may have connectors within the housing. In some applications, the station also may comprise a power lead which may be operatively connected to a subsea installation and a transceiver for communicating data to a desired location, e.g. a surface location. The docking station enables docking with an underwater vehicle used to facilitate the subsea servicing operation.

BACKGROUND

Hydrocarbon fluids such as oil and natural gas are obtained from asubterranean geologic formation, referred to as a reservoir, by drillinga well that penetrates the hydrocarbon-bearing geologic formation. Insubsea applications, the well is drilled at a subsea location andcompleted with the appropriate type of completion equipment. The welland the completion equipment may be serviced via interventionoperations. However, subsea intervention operations tend to be extremelycostly. For example, intervention operations often involve deployment ofa rig, e.g. a semi-submersible rig using tension risers, and thisdeployment is time-consuming and costly. Some subsea interventionoperations also may employ a surface vessel to supply equipment for usein the intervention. In some applications, the surface vessel also maybe used as a platform for the intervention by being precisely positionedover the subsea well during the well servicing operation.

SUMMARY

In general, a system and methodology facilitate subsea well servicing,e.g. intervention operations. The system utilizes a station movablypositioned on a sea floor. The station comprises a housing and a liftingarrangement mounted on the housing to enable lifting of the station.Consequently, the station may be lifted from one subsea location andmoved to another subsea location for a subsequent well serviceoperation. The station further comprises a docking station havingconnectors within the housing. The docking station may be coupled with apower lead operatively connected with a subsea installation for transferof power to the station. In some applications, the station also maycomprise a transceiver for communicating data to a desired location,e.g. a surface location. The docking station enables docking with anunderwater vehicle used to facilitate the subsea intervention operationor other well servicing operation.

However, many modifications are possible without materially departingfrom the teachings of this disclosure. Accordingly, such modificationsare intended to be included within the scope of this disclosure asdefined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the disclosure will hereafter be described withreference to the accompanying drawings, wherein like reference numeralsdenote like elements. It should be understood, however, that theaccompanying figures illustrate the various implementations describedherein and are not meant to limit the scope of various technologiesdescribed herein, and:

FIG. 1 is a schematic illustration of an example of a subsea well systemutilizing a transportable station able to communicate with a variety ofhosts located at the surface or at other suitable locations, accordingto an embodiment of the disclosure;

FIG. 2 is a schematic illustration similar to that of FIG. 1 but showingan example of an underwater vehicle in a different operational positionrelative to the station, according to an embodiment of the disclosure;

FIG. 3 is a schematic illustration of an example of a transportablesubsea station being moved from one subsea location to another,according to an embodiment of the disclosure; and

FIG. 4 is an illustration of an example of a transportable station whichmay be used with a dockable underwater vehicle, according to anembodiment of the disclosure.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of some embodiments of the present disclosure. However,it will be understood by those of ordinary skill in the art that thesystem and/or methodology may be practiced without these details andthat numerous variations or modifications from the described embodimentsmay be possible.

The present disclosure generally relates to a system and methodologywhich facilitate subsea well intervention operations. The systemutilizes a transportable station which may be movably positioned on asea floor. The transportable station is readily coupled with a surfacevessel or other transport vehicle so that it may be lifted from a subsealocation and moved to another subsea location. For example, thetransportable station may be positioned on the seabed proximate a wellto facilitate a well intervention operation. Upon completion of the wellintervention operation, the transportable station may be lifted andmoved to another seabed location to facilitate an intervention operationfor another well.

According to an embodiment, the transportable station comprises ahousing and a lifting arrangement mounted on the housing to enablelifting of the station. The lifting arrangement may be coupled with alift line or other suitable mechanism so the transportable station maybe lifted from one subsea location and moved to another subsea locationfor a subsequent intervention operation or other well servicingoperation. Depending on the location of the subsequent well, the stationmay be lifted to the surface and transported via sea, air, and/or landto the subsequent subsea location. The transportable station may furthercomprise a docking station having connectors within the housing. Thedocking station may be coupled with a power lead which, in turn, may beoperatively connected with a subsea installation for transfer of powerto the station. In some applications, the power lead also may be used tocommunicate data. However, the transportable station may comprise atransceiver for communicating data to a desired location, e.g. a surfacelocation.

The docking station further enables docking with an underwater vehicleused to perform the subsea intervention operation. The underwatervehicle may comprise a variety of controllable underwater vehicleshaving a rechargeable battery or other power supply to power thrustersor other motive devices for moving the underwater vehicle between thestation and the desired subsea installation, e.g. wellhead assembly. Theunderwater vehicle is able to move into the transportable station anddock with the docking station to receive power and/or data. In someapplications, the underwater vehicle may remain docked in thetransportable station while the station is moved from one subsealocation to another.

The system may be used with subsea wells which extend beneath the seafloor. In such an embodiment, the subsea station may be located on thesea floor. An underwater vehicle is housed in the station and is adaptedto service at least one subsea well. The station and underwater vehicleare transportable and may be moved from one subsea well to anothersubsea well not serviceable from the original position of the station.In some applications, the station and underwater vehicle are used toservice wells in a first grouping of subsea wells and then the stationand underwater vehicle are transported together to a second location forservicing wells in a second grouping of subsea wells.

In a specific example, the underwater vehicle comprises a battery whichmay be recharged when the underwater vehicle docks with a dockingstation within the underwater station. While docked, the battery may berecharged for further operation of the underwater vehicle in performingwell service operations and/or other subsea operations. The battery ofthe underwater vehicle may be charged, for example, by power suppliedvia the power lead and/or batteries located on the transportablestation. Various data also may be communicated between the surface andthe station/underwater vehicle while, for example, the underwatervehicle is docked with the station. In some applications, data also maybe communicated when the underwater vehicle is undocked. As described ingreater detail below, the underwater vehicle may comprise various othercomponents, such as sensors used to locate wells, the station, and/orother underwater installations.

In an operational example, the underwater vehicle may be used in a wellintervention operation. According to commands provided from the surface,the underwater vehicle gathers appropriate tools from the station. Theunderwater vehicle is then directed to a desired wellhead correspondingwith the well to be serviced. While at the desired well, the underwatervehicle performs a desired intervention operation before returning toand again docking with the underwater station.

Referring generally to FIG. 1, an example of a subsea well system 20 isillustrated. The subsea well system 20 may be used in a variety ofsubsea applications, e.g. subsea well applications, and comprises astation 22 which is movably positioned on a sea floor 24 or at anothersubsea location, e.g. on a subsea installation. In other words, thestation 22 is transportable from one subsea location to another, e.g.from one sea floor position to another sea floor position, forperformance of subsequent subsea operations.

In the illustrated example, the subsea station 22 comprises a housing 26and a lifting arrangement 28 mounted on the housing 26 to enable liftingand transport of the station 22 between subsea locations. The underwaterstation 22 further comprises a docking station 30 located at leastpartially within the housing 26 and having interfaces 31 to enabledocking and undocking with an underwater vehicle 32. The docking station30 also may be coupled with a power lead 34 which may be selectivelycoupled with various types of subsea infrastructure 36, e.g. a subseainstallation. In some embodiments, the transportable station 22 also maycomprise a power source 37, e.g. batteries, for use by the station 22 torecharge the underwater vehicle 32 and/or for other uses.

By way of example, at least one of the subsea installations 36 maycomprise a wellhead assembly 38 (and associated equipment, e.g. blowoutpreventer and other subsea equipment) positioned generally over a well40 having a wellbore 41 extending into the subsea geologic formation.The subsea installations 36 may be positioned at desired locations alongthe sea floor 24 and may each comprise a subsea installation dockingstation 42 for engagement with underwater vehicle 32. Depending on theapplication, the underwater vehicle 32 may be used for carrying tools,operating equipment, and performing various subsea operations, e.g.intervention operations, with respect to a given well 40. In someapplications, the underwater vehicle 32 may be used for coupling anduncoupling the power lead 34 with the appropriate subsea installation36.

During various operations, command signals and/or other data may becommunicated from the surface to station 22 or from station 22 to thesurface. Accordingly, the station 22 may comprise a transceiver 44 used,for example, to communicate data between the subsea station 22 and ahost 46. By way of example, the transceiver 44 may comprise an acousticor optical transmitter and receiver for sending and/or receiving datawirelessly with respect to the host 46.

The host 46 may comprise various types of hosts and may comprise one ormore of a platform 48, a surface vessel (e.g. a floating productionstorage and offloading vessel) 50, a wave glider 52, an unmanned surfacevehicle 54, e.g. a buoy 55 or other unmanned surface vehicle, or anothersuitable host located at a sea surface 56 or at a suitable submergedlocation. Each host 46 comprises a suitable host transceiver 57 forcommunicating with station transceiver 44. It should be noted thatcommunication data, e.g. commands, may be communicated via transceiver44 and/or over power lead 34. For example, low bandwidth datacommunication may be provided along with power through the power lead34. The power lead 34 also may incorporate other types of communicationlines, e.g. fiber optic communication lines, so that power and data,e.g. underwater vehicle command signals, may be relayed from the subseainstallation 36 to the station 22. Other communication systems also maybe used for communication of data or to supplement communication ofdata.

The underwater vehicle 32 may be constructed in various sizes,configurations, and with several types of components. By way of example,the underwater vehicle 32 may comprise a battery 58, e.g. a rechargeablebattery pack, a sensor 60 (or several sensors 60), and a vehicle dockingassembly 62. The vehicle docking assembly 62 is configured for dockingand undocking with respect to docking station 30 of subsea station 22.

The sensor or sensors 60 may be used to guide the underwater vehicle 32to the desired well 40, e.g. to the desired wellhead assembly 38, or toother subsea infrastructure 36 under the power of battery 58. By way ofexample, the sensor(s) 60 may comprise a laser sensor or other type oflight sensor which tracks light from a given light source on the desiredsubsea infrastructure, e.g. the subsea wellhead assembly 38, so thatcontrol signals may be provided to suitable thrusters 64 or other motiveunits. In this type of example, the battery 58 may be used to powerthrusters 64 or other types of motive units which may be selectivelyoriented or which may work in cooperation with controllable guide vanesto direct the underwater vehicle 32 along a desired path.

Based on data from the sensor/sensors 60, an internal controller may beused to control thrusters 64, e.g. side thrusters and end thrusters, toguide the underwater vehicle 32 to a desired location. Examples ofsuitable underwater vehicles 32 may be based on remotely operatedvehicles (ROVs) or other controllable underwater vehicles such as theunderwater vehicle described in U.S. Pat. No. 6,808,021. Additionally,the underwater vehicle 32 may comprise a variety of tool graspingdevices, tool storage devices, torque arms, grappling devices, roboticarms, and/or other features selected to enable a desired interventionoperation or other subsea operation.

With additional reference to FIG. 2, the underwater vehicle 32 isillustrated as having undocked from station 22 and moved via thrusters64 to a well 40. By way of example, the underwater vehicle 32 may beguided via at least one of the sensors 60 into docking engagement withthe desired subsea installation 36. However, the underwater vehicle 32may be operated in cooperation with the subsea installation 36 in avariety of other ways to facilitate a given well servicing operation,e.g. intervention operation.

In some embodiments, at least one of the sensors 60 may be in the formof a light sensor used to track a light source on the desired subseainstallation 36. The light sensor 60 provides sensor data to a suitablevehicle controller, e.g. microprocessor, to enable control overthrusters 64. Thrusters 64 may be controlled so as to direct theunderwater vehicle 32 into engagement with installation docking assembly42 or to another suitable position for interaction with well 40 or othersubsea infrastructure 36. In some operations, the underwater vehicle maybe used to provide a desired tool or other equipment for use in anintervention operation with respect to the well 40.

When a given operation is completed with respect to well 40 or a groupof wells 40, the underwater station 22 may be moved to anotherunderwater location for servicing of other wells. By way of example, alift line 66 or other suitable mechanism may be coupled with liftingarrangement 28 of station 22. The station 22 is then lifted from asubsea location, e.g. from a location on sea floor 24, and moved toanother desired location, e.g. another location along see floor 24. Itshould be noted the station 22 also may be transported from and/or tosubsea locations on subsea infrastructure 36, e.g. on subseainstallations.

In the embodiment illustrated, lift line 66 also is connected with asurface vessel 68 via, for example, a winch 70 or other suitable liftingdevice. The lifting device/winch 70 may be operated to lift the station22 from its position on sea floor 24. This enables the surface vessel 68to move the station 22 to a subsequent subsea location. Depending on thedistance station 22 is to be moved, the station 22 potentially can bemoved through water or lifted to the surface vessel 68 for transport. Insome operations, the station 22 may be placed on another vessel fortransport by sea or by air to another subsea well site. Here, thestation 22 may be deployed to the subsequent subsea location forservicing additional wells 40.

The station 22 may be transported alone or with the underwater vehicle32 disposed within housing 26 of station 22, as illustrated. Forexample, the underwater vehicle 32 may be powered via thrusters 64through an opening 72 in housing 26 and guided into docking engagementwith docking station 30 for transport. In some operations, theunderwater vehicle 32 may first be used to disconnect power lead 34 fromthe corresponding subsea installation 36. However, other methods ofdisconnecting power lead 34 also may be employed to enable transport ofstation 22.

Referring generally to FIG. 4, an embodiment of station 22 isillustrated in greater detail. It should be noted the station 22 mayhave a variety of other and/or additional components and features toaccommodate parameters of a given operation and/or environment. In theillustrated example, the subsea station 22 comprises housing 26 withgenerally rectangular sides and having opening 72 located at one end.However, the housing 26 may be constructed with various other shapes,e.g. semi-cylindrical shapes, to accommodate different types ofunderwater vehicles 32.

In the example illustrated, lifting arrangement 28 comprises a pluralityof lugs 74 having attachment features 76, e.g. openings, to which thelift line 66 or other lifting mechanism may be attached. The pluralityof lugs 74 may comprise four lugs 74 positioned in corners of thehousing 26, as illustrated. However, different numbers and arrangementsof lugs 74 may be used to enable lifting and transport of station 22. Insome applications, the lugs 74 may be replaced or supplemented withvarious other features of lifting arrangement 28.

As illustrated, the docking station 30 is positioned at least partiallywithin housing 26. By way of example, the docking station 30 may belocated within housing 26 and the power lead 34 may be routed from theinternal docking station 30, through a wall of housing 26, and to anexterior of housing 26 for coupling with a suitable subsea installation36 or other subsea equipment. The docking station 30 may comprise aconnector 78 or a plurality of connectors 78 to which the power lead 34is coupled for supplying power and/or data communication.

By way of example, connectors 78 may comprise power connectors to whichelectrical conductors of power lead 34 are coupled so as to supplyelectrical power to docking station 30. The power may be used torecharge battery 58 and/or to provide electrical power for other useswith respect to the underwater vehicle 32 and station 22. In someembodiments, at least one of the connectors 78 may be used forcommunication of data to or from the underwater vehicle 32 when, forexample, transceiver 44 is not used or as a supplement to transceiver44.

Depending on the type of application, the power lead 34 may comprise anelectrical flying lead adapted to connect to the desired subseainfrastructure, such as the desired subsea installation 36. The powerlead 34 may be used for coupling with subsea trees, subsea manifolds,electrical termination units, existing field control systems, or othersubsea installations. The power lead 34 receives power from the existingsubsea architecture, e.g. the subsea installation 36 to which it isattached. In some embodiments, the power lead 34 also may be configuredto receive communication data from the existing subsea system byincorporating fiber optics or other data transmission media. Theunderwater vehicle 32 or another suitable underwater device may be usedto engage the power lead 34 with the subsea installation 36 and todisengage the power lead 34 when the station 22 is moved to anotherlocation.

The docking station 30 also may comprise a guide structure 80 whichworks in cooperation with connectors 78 so as to facilitate easy dockingand undocking of underwater vehicle 32. In this example, the connectors78 and guide structure 80 serve as interfaces 31 to facilitate thedocking and undocking. By way of example, the underwater vehicle 32 maybe guided through opening 72 and towards docking station 30 via one ormore emitters 82, e.g. light sources, cooperating with a correspondingsensor or sensors 60 of the underwater vehicle 32. The underwatervehicle 32 is moved into station 22 via, for example, thrusters 64 untilengaging guide structure 80. The guide structure 80 ensures propercoupling of the vehicle docking assembly 62 with connectors 78. Itshould be noted the station 22 also may comprise an additional emitteror emitters 83, e.g. a light source, positioned along the exterior ofhousing 26 so as to initially guide underwater vehicle 32 to the generalvicinity of station 22 for docking.

Depending on the parameters of a given operation, e.g. well interventionoperation, the subsea station 22 may comprise various other features.For example, the station 22 may comprise internal tool storage areas 84located along a floor of housing 26. Additionally, the station 22 maycomprise storage bins 86, vertical racks 88, horizontal racks 90, and/orother features to accommodate storage of tools 92 and/or other devices.By way of example, the tools 92 may be well intervention tools which maybe selected and utilized by underwater vehicle 32 during a wellintervention operation on a desired well 40.

In a well intervention operation, for example, the underwater vehicle 32may be sent suitable commands via transceiver 44 and/or power lead 34.Based on this command data, the underwater vehicle 32 gathersappropriate tools 92 from station 22 and then undocks from dockingstation 30. The underwater vehicle 32 then moves via thrusters 64 to theappropriate wellhead assembly 38 corresponding with the well 40 in whichthe intervention operation is to be performed. In some operations, theunderwater vehicle 32 may dock with the corresponding installationdocking assembly 42 to perform the intervention operation. Once theintervention operation is completed, the underwater vehicle 32 returnsto station 22 and docks with docking station 30 to, for example,recharge battery 58.

If the overall intervention operations are finished, the lift line 66may be coupled with lugs 74 via underwater vehicle 32 or via anothersuitable underwater device. Subsequently, the station 22 (or the station22 with internal underwater vehicle 32) may be lifted and moved to asubsequent location for additional well servicing operations. Once atthe subsequent location, the station 22 is positioned on the sea floor24 (or at another suitable subsea location) to enable operation ofunderwater vehicle 32 with respect to a corresponding well or wells 40.

Depending on the specifics of a given use, the shape, size, and featuresof station 22 may be adjusted. For example, station housing 26 may havevarious shapes to accommodate different types of underwater vehicles 32.Similarly, the station 22 may use a variety of lifting assemblies,docking stations, guiding lights or other emitters, transceivers, andtool storage features. The station 22 also may incorporate additionaldevices or features to accommodate aspects of different types of wellservicing operations. The base of housing 26 may be constructed forresting on various types of sea floor materials and/or engaging varioustypes of subsea installations.

Although a few embodiments of the disclosure have been described indetail above, those of ordinary skill in the art will readily appreciatethat many modifications are possible without materially departing fromthe teachings of this disclosure. Accordingly, such modifications areintended to be included within the scope of this disclosure as definedin the claims.

What is claimed is:
 1. A system for use in a subsea operation,comprising: a station movably positioned at a subsea location, thestation comprising: a housing; a lifting arrangement coupled to thehousing to enable repeated coupling of the lifting arrangement with alift line as the station is sequentially transported from one subsealocation to another for a plurality of well servicing operations; and adocking station having interfaces for an underwater vehicle receivablewithin the housing.
 2. The system as recited in claim 1, furthercomprising the underwater vehicle dockable with the docking stationwithin the housing.
 3. The system as recited in claim 2, wherein thestation further comprises a power lead coupled to the docking stationand a transceiver for communicating data wirelessly.
 4. The system asrecited in claim 3, further comprising a host, the transceivercommunicating data between the station and the host.
 5. The system asrecited in claim 1, wherein the station further comprises batteries forsupplying electrical power.
 6. The system as recited in claim 2, whereinthe underwater vehicle comprises a sensor to detect subsurfaceequipment.
 7. The system as recited in claim 2, wherein the underwatervehicle comprises a sensor to detect a subsea infrastructure.
 8. Thesystem as recited in claim 2, wherein the underwater vehicle comprises abattery to power the underwater vehicle when it leaves the dockingstation.
 9. The system as recited in claim 2, wherein the transceivercomprises a transmitter for transmitting data wirelessly to a hostlocated on the surface.
 10. A system as recited in claim 4, wherein thehost comprises a surface vessel.
 11. A system, comprising: an underwatervehicle; and a transportable station for positioning proximate a seafloor, the transportable station comprising a housing and a dockingstation having a power coupler, the docking station being positioned fordocking with the underwater vehicle when the underwater vehicle entersthe housing, the transportable station further comprising a liftingarrangement by which the transportable station and the underwatervehicle may be lifted and moved from one subsea location to anothersubsea location.
 12. The system as recited in claim 11, wherein thetransportable station further comprises a transceiver for communicatingdata between the transportable station and a host.
 13. The system asrecited in claim 12, wherein the host comprises a platform.
 14. Thesystem as recited in claim 12, wherein the host comprises a surfacevessel.
 15. The system as recited in claim 12, wherein the hostcomprises a buoy.
 16. The system as recited in claim 12, wherein thehost comprises an unmanned surface vehicle.
 17. The system as recited inclaim 11, wherein the transportable station further comprises a powerlead coupled with the power coupler, the power lead being selectivelyconnectable to a subsea installation to enable delivery of electricalpower from the subsea installation to the transportable station.
 18. Amethod, comprising: placing a transportable station on a sea floor;docking an underwater vehicle to a docking station within a housing ofthe transportable station; coupling a lift line to the transportablestation; lifting the transportable station from the sea floor; andmoving the transportable station to another location on the sea floor.19. The method as recited in claim 18, further comprising powering thetransportable station from a subsea installation.
 20. The method asrecited in claim 18, further comprising undocking the underwater vehiclefrom the docking station and directing the underwater vehicle to asubsea infrastructure.